It is the purpose of this one year supplemental proposal to begin a study of the fluorescent properties of elastin in order to determine the physical and chemical peculiarities of this protein which are responsible for fluorescence. Very recent findings regarding the primary structure of elastin have led us to propose an exciting hypothesis regarding its autofluorescence. This hypothesis states that the close proximity of tyrosine to the crosslinks desmosine and asodesmosine, in the insoluble protein produces fluorescence. Because the precursor protein, tropoelastin, does not fluoresce, we propose that monitoring of fluorescence may prove to be an extremely important and sensitive tool in following the elastin crosslinking process in vitro. These studies of the molecular basis of fluorescence are thus meant to serve as a ground work for such future in vitro studies. Using elastin purified by newly developed methods we plan to explore the fluorescent spectra of a variety of elastins and elastin peptides, and also to study the effects of chemical modification of various amino acids residues in elastin on fluorescence. We also plan to study individual interactions between such amino acids as tyrosine and desmosine in solution as expressed by fluoresence or lack of fluorescence. It is anticipated that these studies will ultimately lead to a much better understanding of the molecular basis of elastin formation in blood vessels.